Mobile phones, which are mobile communication devices, are predominantly folding-type these days. A key-lock function has been implemented to prevent the mistaken-operation of keys arranged on an exterior of a mobile phone that has been folded and put inside a bag. This key-lock function disables the operation of keys on the exterior of the mobile phone in a closed state as a result of a specified key on an operation surface with number keys and the like being pressed when the mobile phone is in an opened state. In order to operate the external keys, the mobile phone must be opened and the specified key must be pressed again to cancel the key operation disablement setting.
Other examples of key locking methods are disclosed in patent documents 1 and 2.
It is to be noted that the functions of mobile phones include not only the conventional calling function, but also emailing, web page browsing, and even FM receiving functions.
For example, mobile phones with an FM receiving function are provided with an external key for adjusting the volume. If a user listening to an FM broadcast wants to adjust the volume while the key-lock function is enabled, they must open the mobile phone, cancel the key-lock function, and again enable the key-lock function after adjusting the volume.
Patent document 1: Japanese Patent Application Publication No. 2000-32098
Patent document 2: Japanese Patent Application Publication No. 2001-285442